1. Biological Control of Insect Pests

2. Bio-pesticides Advantages: Low mammalian toxicity;
Minimal effect on beneficial insects;
Fast action and breakdown
High selectivity
Low phytotoxicity.
Types:
Substances of plant origin (botanicals).
Substances of animal origin.
Microorganisms-based bio-pesticides.

3. Definition of biological control

4. Biological control definition
Biological control can be defined as the use of natural enemies to reduce the damage caused by a pest population. Biological control is an approach that fits into an overall pest management program, and represents an alternative to pesticides.

5. Biological control definition
The "who": The natural enemies themselves that is to say predators, parasitoids and pathogens.
The "what": The objective to achieve which can be prevention, reduction or delay of infestation.
The "how": The approach that is taken with the natural enemy to achieve the objective which can be conservation, augmentation or importation.

6. Basic biological control theory
Understanding the major concepts of natural control is key to understanding how natural enemies control pests and how they can be used in biological control programmes.

7. Biological control agents: parasitoids, predators and pathogens.

8. Macro-organisms use in biocontrol
(Copping, 2004)

9. Phytophagous biocontrol agents
(Copping, 2004)

10. Parasitoids

11. Parasitoids
Parasitic insects (also known as parasites and parasitoids) are insects whose immature stages (larvae) develop by feeding on or in the bodies of their host arthropods, which are usually other insects.
Host: The organism attacked and used as a food source by the parasite.
Parasites: are organisms that live in or on , and at the expense of other organisms (host). The parasite provides no benefit to the host, which is weakened or damaged, and eventually destroyed or unable to reproduce. Parasitic insects are unique, because it is the immature stages that kill the host.

12. Parasitoids
Nearly all parasite immatures develop on or in a single host.
Parasites are holometabolous, having complete development (egg, larval, pupal and adult stages).
Adult parasites are free living; some species will feed on hosts (predators), in addition to ovipositing in or on the hosts.
In the world of parasites, only females are significant players, as they are the ones that find and attack hosts. For some species, males are not known to exist.

13. Parasitoids types Where the egg is laid
(inside the host = endoparasite
outside the host = ectoparasite).

14. Parasitoids types The feeding habit of the immature stage:
Egg parasite: Parasite adult attacks the host egg, and the parasite progeny emerge from the egg.
Egg-larval parasite: Parasite adult attacks the host egg, but the parasite progeny emerge from the larva.
Larval parasite: Parasite adult attacks the host larva, and the parasite progeny emerge from the larva.
Larval-pupal parasite: Parasite adult attacks the host larva, but the parasite progeny emerge from the pupa.
Pupal parasite: Parasite adult attacks the host pupa, and the parasite progeny emerge from the pupa.

15. Parasitoids types Number of parasites’ progenies :
Multiparasitism: A single host is attacked by more than one species of parasites.( when females of more than one species oviposit in individual host)
Superparasitism: Several females of one species of parasite attack the same host, female oviposits more than one egg to a host than can successfully develop to maturity.

16. Parasitoids types Hyperparasitism
Hyperparasitism is a multilevel trophic system in which one species develops as a parasitoid of another parasitoid.
The species attacking the free living organisms (herbivore) is called a primary parasitoid, the primary parasitoid is attacked by a secondary parasitoid.

17. Parasitoids taxonomy
Although parasitism is found in several insects orders, primary orders of parasites are Hymenoptera and Diptera.
The greatest diversity of parasites is found in Hymenoptera.
The most important parasitic families within Hymenoptera e.g wasps.
Several Diptera families have members that are parasitic:

18. At least species of Hymenoptera are parasitoids, but only 765 species have been used in biological control programs worldwide.

19. A tiny wasp injects eggs into a plant bug nymph

20. Wasp larvae coming out of a caterpillar

21. Predators

22. Predators
Predation can be defined as a trophic level interaction in which one species derives energy from the consumption of individuals of another species.
A predator is considered an entomophagous species that generally consumes more than one prey individual to complete its development.
Over 16 orders of insects contain predaceous members, in approximately 200 families. Including spiders and mites, there are probably in excess of 200,000 species of arthropod predators.

23. Predators
Among the non-insect arthropods, spiders (Araneae) . Spiders have been little utilized in biological control.
Mites (Acari) have a number of predaceous members. Mites have been used in a number of biological control projects.
Monophagy: The predator may feed on one or a very limited number of species within the same genera.
Oligophagy: Predators feed primarily on aphids preys, or on whiteflies or scales.
Polyphagy: A broad prey range, may include plant materials (fluids, nectars, pollen), insects and fungi.

24. Predators’ characteristics
kill and consume more than one prey organism to reach maturity.
Relatively large size compared to prey.
Predaceous as both larvae and adults.
Diet may be influenced by:
Prey environment.
Competition with other predators.
Suitability of prey.

25. Preys location and capture
Strategies used by predators to locate and capture preys include the following:
Directed searching: Movement may be guided by features of the environment that increase chances for encountering prey.
Active searching: Use of visual to orient to prey at a distance.
Ambushing: Waiting for prey , e.g. raptorial legs (praying mantids) they clasp their preys.
Trapping: Neuropterans prepare conical pits in loose sand, larvae wait at the bottom with large sickle shaped jaws.
Attracting: Lightning bugs, flashing of one species to attract males of another. Females then consume males.

26. Predators groups
(Copping, 2004)

27. Predatory insect groups
The major groups of predaceous insects belong to the following orders: Coleoptera, Dermaptera, Diptera, Hemiptera, Hymenoptera, Mantodea, Neuroptera, Orthoptera and Thysanoptera.  
Coleoptera:
Coleoptera (beetles and weevils) is the largest order in the class Insecta.
Many Coleoptera species are herbivores, others live on fungi but many beetles are predators. There are even few parasitic beetles.
The most important Coleoptera predaceous families are the following: (ground beetles); (tiger beetles), (soldier beetles) and (ladybird beetles).

28. Predatory insect groups
Dermaptera:
Members of the order Dermaptera are recognized by pincers at the tip of the abdomen. These structures are used to hold prey while it is being consumed.
The predaceous species feed on soft bodied insects (e.g. aphids, leaf hoppers, larvae of Coleoptera and Lepidoptera).
The most important Dermaptera predatory are: (spine tailed earwigs)

29. Predatory insect groups
Diptera:
Some flies are predators of other arthropods (e.g., robber flies), but most of them are external parasites (e.g., mosquitoes and deer flies).
Hemiptera:
The most Hemiptera predatory are: assassin bugs, stink bugs.

30. Predatory insect groups
Hymenoptera
Hymenoptera is one of the larger orders of insects, includes sawflies, wasps, bees, and ants.
Females of Hymenoptera typically have a special ovipositor for inserting eggs into hosts or otherwise places, often modified into a stinger.
The most important Hymenoptera predaceous groups are: wasps and ants.

31. Predatory insect groups
Neuroptera:
The insect order Neuroptera includes the antlions.
The adults of this order possess chewing mouthparts, and most are predatory.
Orthoptera:
The Orthoptera order includes the grasshoppers, crickets and locusts.
The most important Orthoptera predaceous species are included Omnivorous on soft bodied insects, aphids and scales.

32. Predatory insect groups
Thysanoptera:
Most species of Thrips feed on plant tissues .
The most important Thysanoptera predatory is Banded thrips.
Mantodea:
Mantids have elongate bodies that are specialized for a predatory lifestyle: long front legs with spines for catching and holding prey, a head that can turn from side to side.
The most important predaceous is praying mantid.

33. Predator-prey interactions
Prey habitat location:
Olfactory and visual are likely used by adult predators to locate suitable habitats.
Volatile are known to be used as attractants by selected insect predators.
For some predatory species, a blend of compounds, including volatiles from the plants in the habitat as well as prey volatiles, are involved. This blend is called synergistic mixture of plant and prey derived.

34. Predator-prey interactions
 Prey location:
Physical and chemical are used by many predatory species to locate prey. Vision may be important for ambush type predators or other predators of slow-moving prey.

35. Predator-prey interactions
 Prey acceptance:
The following may influence prey acceptance: size of prey and composition of cuticle.
Morphological and physiological factors can influence prey acceptance.
Size, shape, movement, and external and internal chemical of prey are factors that can be used as stimuli to induce prey acceptance.

36. Predator-prey interactions
 Prey acceptance:
Physical factor that influences prey acceptance is the size of prey relative to the predator.
Prey integumentary chemicals (e.g., waxes) may serve as phagostimulants for some predatory species.
Some prey (e.g. aphids) kick, run, drop, or fly away, or noxious chemicals.

37. Rove beetles eating a maggot

38. Sub phyllum chelicera Composed of three classes of over 63000 species.
The most important class with regarded to applied biological control is the Arachnida, divided into 13 orders, we will consider only the two most important, the Araneae (spider) and Acariformes (mites)

39. Spider Carnivore Have long life cycle
Do not have distinct performance for a given prey species.
Increase in attacks occurs in response to increasing prey density.

40. A scorpion eating a cricket

41. A spider eating an insect.

42. A lacewing larva eating an aphid
Howard Russel, Michigan State University

43. A spider eating a moth

44. A big-eyed bug glues a whitefly to a leaf and eats it.

45. Pathogens

46. Pathogens
Associations between Microorganisms and insects range from mutualistic associations to those where the microorganism causes fatal disease in the insect host.
Infectious insect diseases, usually causing effects in the host, occur frequently in insects and often act as important natural control agents.
Insect pathogens are most often viewed as microbial insecticides.

47. Pathogens
Entomogenous: Organisms growing in or on the bodies of insects; usually a parasitic or other intimate symbiotic relationship.
Entomophagous: Insectivorous; the consumption of insects and their parts.
Entomophilic: Associations between insects and other organisms, e.g. plant, microorganisms, Protozoa, and nematodes.
Horizontal transmission: Transmission of a pathogen from infected individuals to another
Vertical transmission: Transmission of a pathogen from one generation of host to the next.

48. Pathogens
Invasion/Infection: Invasion is the entry of a microorganism into the host body. Primary invasiveness is a property of pathogenic microorganisms.
Latent infection: Unapparent infection; the pathogen is in a non-reproductive phase and a pathogen-host equilibrium is established.
Pathogenicity : Pathogenicity is the ability of an organism to invade the host and cause disease.

49. Beaveria bassiana Fungal insecticides Grows naturally in soils
Acts as a parasites on various insect species causing white muscardine disease
Belong to entomopathogenic fungi

51. Used as a biological insecticide to control a number of pests such as termites, whitefly, different beetles such as colorado potato beetle
Grows as white mould on most cultural media.

52. Mechanisms
When the microscopic spores of the pathogen come into contact with the body of an insect host , they germinate , penetrate the cuticle and grow inside, killing the insect within few days.

53. Some fungi invades both the outer surface of cuticle and digestive tract of insects.
Fungi secrets myocotoxins (low molecular weight) that kill insects.
Beauvercin =phenyl alanin and 2-hydroxy-N methyl isovaleric acid
This toxin alterate of permiability of plasma membrane , lead to leak out of electrolytes and water

54. Metarhizium spp produce two toxins
Destruxins which cause damage of mitochondrial membranes.
Cytochasins which cause immune suppression on immune system of insects.

55. يتم قتل الحشرة عن طريق الاستهلاك المباشر في الجسم (تظهر الهيفات الداخلية بشكل كثيف داخل الحشرة و بعد استخدام بقايا جسم الحشرة يتم موت الغزل الفطري نتيجة لفقد المواد الغذائية و يتجرثم الفطر و يصبح مصدر عدوى مستقبلية

56. Verticillium lecanii Cosmopolitan fungus found on insects
Common pathogen of scale insects
The conidia are slimy and attach to the cuticle of insects
The fungus infects insects by producing hyphae germinating spores that penetrate the insects integuments, the fungus destroy the internal contents and insects dies.
Control of larvae and adult stages of coleoptera.

58. Baculovirusesas biocontrol agent

59. Baculoviruses are pathogens that attack insects and other arthropods.
They are usually extremely small and are composed primarily of double-stranded DNA

60. Because this genetic material is easily destroyed by exposure to sunlight or by conditions in the host's gut, an infective baculovirus particle (virion) is protected by protein coat called a polyhedron .
Most insect baculoviruses must be eaten by the host to produce an infection, which is typically fatal to the insect.

61. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus, so "baculovirus" or "virus" will hereafter refer to nucleopolyhedroviruses
These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications.

62. They have been shown to have no negative impacts on plants, mammals, birds, fish, or even on non-target insects
This is especially desirable when beneficial insects are being conserved to aid in an overall IPM program, or when an ecologically sensitive area is being treated.

63. Life Cycle - Viruses are unable to reproduce without a host
- They are obligate parasites.
- Baculoviruses are no exception.
- The cells of the host's body are taken over by the genetic message carried within each virion, and forced to produce more virus particles until the cell, and ultimately the insect, dies.
- Most baculoviruses cause the host insect to die in a way that will maximize the chance that other insects will come in contact with the virus and become infected in turn.

66. Infection begins when a larva eats a proteinaceous occlusion body, containing many virus envelopes. Each envelope contains a mixture of viral genomes, some of which can contain deletions. The occlusion body dissolves in the larval gut, releasing the enveloped viruses, which establish a primary infection in the midgut cells. The infected midgut cell first produces single viral genomes that bud from the cell surface and infect other cells — it is estimated that around four virus genomes invade each cell during this secondary infection. As viral multiplication continues within the infected cell, occlusion bodies form. After many host cells have been infected, the virus turns on genes that liquefy the host, releasing occlusion bodies, which are eaten by new hosts.

68. Baculoviruses as biocontrol agents
Baculoviruses are rod-shaped, double stranded DNA viruses that can infect and kill a large number of different invertebrate organisms
Baculoviruses have limited host ranges and generally do not allow for insect resistance to develop
Slow killing of target insects occurs
In order to speed killing (enhance effectiveness), several genes can be expressed in the baculovirus including diuretic hormone, juvenile hormone esterase, Bt toxin, scorpion toxin, mite toxin, wasp toxin, and a neurotoxin

69. The top caterpillar is infected with a virus.

70. Limitations 1- Relatively slow speed of kill.
2- Narrow spectrum of activity
3- little residual activity

71. Bacteria as biocontrol agent
Most widely and successfully in insect control
1- easy to mass produce
2- easy to formulate
3- easy to use in large scale
4- kill target insects quickly
5- have a spectrum of activity that includes many economically important pests
6- safer than most synthetic chemical pesticides fot non target organisms and the environment

72. There are two major types of bacteria that are used in insect control
1- Cause fatal infectious diseases
e.g. B. popilliae
2- Kill insects primarily through the action of insecticidal toxins.
e.g B. thuringiensis

73. Bacillus thuringiensis is a soil bacterium that produces a toxin (Bt toxin or Cry) that kills certain insects
The Bt toxin or Cry is produced when the bacteria sporulates and is present in the parasporal crystal
Several different strains and subspecies of B. thuringiensis exist and produce different toxins that kill specific insects

74. Some properties of the insecticidal toxins from various strains of B
Some properties of the insecticidal toxins from various strains of B. thuringiensis
Strain/subsp.
Protein size
Target Insects
Cry #
berliner
kDa
Lepidoptera
CryI
kurstaki KTP, HD1
entomocidus 6.01
aizawai 7.29
aizawai IC 1
135 kDa
Lepidoptera, Diptera
CryII
kurstaki HD-1
71 kDa
tenebrionis (sd)
66-73 kDa
Coleoptera
CryIII
morrisoni PG14
kDa
Diptera
CryIV
israelensis
68 kDa

75. The Cry protein: mode of action
The Cry protein is made as an inactive protoxin
Conversion of the protoxin (e.g., 130 kDa) into the active toxin (e.g., 68 kDa) requires the combination of a slightly alkaline pH ( ) and the action of a specific protease(s) found in the insect gut
The active toxin binds to protein receptors on the insect gut epithelial cell membrane
The toxin forms an ion channel between the cell cytoplasm and the external environment, leading to loss of cellular ATP and insect death

76. Isolation & genetic engineering of Cry genes
The Cry (or protoxin) genes are encoded by plasmid DNA, not by chromosomal DNA in B. thuringiensis
Cry genes were expressed in B. thuringiensis under the control of the promoter (rather than its sporulation-specific promoter) and provided increase yield
Constructs have also been produced to enhance toxin action and/or expand its specificity

77. A potential problem with Cry: development of insect resistance (and how to prevent it)
Production of hybrid Bt toxins
Stacking of Bt toxin genes
Use of Bt toxins in combination with other insecticidal proteins such as chitinase and Cyt1A
In plants, the planting of crop buffer zones with non-genetically engineered Bt plants to maintain an insect susceptible population

79. Bacillus popilliae
Control of Japanese beetle larvae in turf since the 1940s.
Several commercial products are available.
The bacteria, usually applied to the soil, cause "milky disease.”
Milky disease spores may reproduce within the beetle larvae and establish a resident population capable of causing mortality over several seasons if the soil is sufficiently warm and moist through the summer months.
It may take several seasons for the disease to control the pest, and it is preferable to treat a broad area to reduce the impact of immigrating healthy beetles.

81. Bacillus sphericus
Is active primarily against mosquitoes belonging to the genera Culex and Anopheles, and exhibits only minor toxicity to most Ades species and blackflies.
The toxicity of Bs like Bt is due to protein endotoxins that are produced during sporulation and assembled into parasporal bodies.
The most toxic strains encode two proteins, one of 51.4 KDa and another of 41.9 KDa
These are proteolytically activated in the mosquito midgut to release peptides of 43 and 39 KDa respectively.
Like Bt, the target of action is midgut epithelium. The toxins bind to micrvilli, causing hypertrophy and lysis of cells.

84. Micro-organisms use in biocontrol
(Copping, 2004)

85. Micro-organisms use in biocontrol
(Copping, 2004)

86. Pathogens Insect viruses:
Viral diseases have been found in 13 insect orders and most likely occur in all orders. Viruses that are primarily or exclusively found in insects are currently placed in 12 families .
DNA Viruses: Baculoviruses (Nuclear polyhedrosis viruses- NPV and Granuloviruses-GV).
RNA Viruses: Reoviruses (Cytoplasmic polyhedrosis viruses). Bacterial pathogens:
They can be divided into two broad categories, non-spore-forming bacteria and spore-forming bacteria.
Although most of the species isolated from diseased insects are non-spore-forming, spore-forming bacteria in the genus Bacillus are the most important from of biological control.

87. Fungal pathogens:
Entomopathogenic fungi are able to invade their insect hosts by penetrating directly through the cuticle.
The fungal spore first adheres to the cuticle.
Under appropriate conditions the spore germinates, penetrates the cuticle of the host and enters the hemocoel.
Fungal reproduction occurs in the hemocoel of the insect host.
As the hemocoel becomes filled with hyphal bodies, the insect usually dies and the fungus continues to develop saprophytically.
After the body of the dead insect is filled with mycelia, fruiting structures and produce infectious spores.
Dead insect has the consistency of a moist loaf of bread and, depending on the colour of the spores or conidia, may appear white or some darker colour.

88. Fungal pathogens:
8 classes, 13 orders and 57 genera that contain entomopathogenic species of fungi.
The Zygomycota and the Ascomycota contain common insect pathogens that are also useful in biological control programs.
Microsporidia:
Microsporidia are important primary pathogens of insects.
Their best use will probably be as augmentatively released or classical biological control agents, not as pesticides.
e.g. Nosema locustae

89. Protozoa:
Of some 14,000 described species of Protozoa, about 500 are pathogens of insects. Many are chronic pathogens that may debilitate a host without producing obvious disease symptoms but some species are extremely virulent, causing stunted growth, slow development, and early death.
Entry into the host is typically by ingestion, but some can invade through the cuticle.
Some species may be transversally transmitted from infected females to their offspring.
Some protozoans exhibit tissue tropism, infecting only certain tissues or organs, others are systemic.

90. Protozoa:
No toxins have been found to be associated with protozoa in insects.
Death or debilitation of infected hosts may be, for example, the result of competition for metabolites, disruption of normal cell and tissue function, or blockage of the gut or other organs .
The insect-pathogenic Protozoa are currently recorded from four major groups: Amoebas, Flagellates and Ciliates.

91. Protozoa
The single cell Microsporidium protozoan infects and naturally controls over 90 species of grasshoppers
Obligate intracellular parasites
Grasshoppers stop feeding, become lethargic and die after feeding on Nosema

92. Trypanosoma lewisi Present in rats blood
Infect of midgut epithelial cells in flea
Kill the nymph of flea within 3-4 days

93. Malpighamoeba locusta
Control of grasshoppers

94. Nematodes:
Some entomogenous nematodes have characteristics that allow them to be considered with the pathogens.
The most important insect pathogenic nematodes for biological control are very small and use mutualistic bacteria to kill the host.

95. Species in the genera Steinernema
Nematodes:
Although nematode species in at least 20 families are primary or facultative parasites of insects, those in the order Rhabditida have been most exploited as biological control agents.
Species in the genera Steinernema
Entomopathogenic nematodes enter the host via natural body openings or through the cuticle.
Others by ovipositing on the host food source and the eggs hatch in the host midgut.
Effects of nematode parasitism on the hosts can be sterility,, reduced mobility and life span, behavioural and morphological changes, and death.

96. Nematodes
Beneficial nematodes seek out and kill the immature stages of harmful soil insects before they become adults.

97. Steinerema feltiae
Entomopathogenic nematode applied for the larval control of several flies species and some moth of larvae.
Penetrate actively insect body through the cuticle
A pathogenic symbiotic Xenorhabdus is responsible for the rapid host killing (24-72)hr release toxins or proteases

98. Steinerema feltiae showed promising results for the biological control of fruit flies.
Steinerema feltiae enter their host through natural openings and rarely through the direct penetration of host cuticle.

101. Plant resistance to insects
History
Wheat cultivars are resistance to hassian fly.

102. Apple cultivars that were resistant to the wooly apple aphid.

103. Categories of resistance
Antibiosis
Antixenosis
Tolerance
1. Antibiosis describes a plant trait that adversely affect the biology of an insect when the plant is used for food.

104. 2. Antixenosis
A property of the plant that makes it not attractive to some feeding or ovipositing insects.

105. 3. Tolerance
Is resistance in which a plant is able to withstand or recover from damage caused by insect pest abundance equal to that damaging a plant without resistance characters (susceptible).

106. Morphological factors include :
Glandular (sticky substance, physical barrier and toxic constituents)
Surface waxes
Tightly packed vascular bundles
A high fiber content

110. Leaves normally release small quantities of volatile chemicals, but when a plant is damaged by herbivorous insects, many more volatiles are released.
The chemical identity of the volatile compounds varies with the plant species and with the herbivorous insect species.
These volatiles attract both parasitic and predatory insects that are natural enemies of the herbivores.
They may also induce defense responses in neighboring plants.

111. Detrimental phytochemical factors include:
Toxins
Prevent feeding and oviposition
Repellents
High concentration of indigestible substances such as lignin and silica
Absence of essential nutrients

112. Antixenotic resistance functions by altering the :
1- Olfactory :Producing affective inhibitors odors that confuse and alter pests
2- Visual
3- Tactileتذوق

113. Tolerance
Tolerance describes properties that enable a resistant plant to yield more biomass than an susceptible plant, due to the
1. Ability to withstand
2. Recover from insect damage caused by insect populations .
3. Outgrowth on insect infestation or removal of damaged tissues

114. Transgenes
Insect pest management systems now have an additional type of insect resistance gene from a non plant source.
Genes from the bacteria Bacillus thuringiensis encoding various delta- endotoxin insecticidal proteins have effective and specific insecticidal effects against Coleoptera and Lepidoptera larvae.

115. Transgenes The Bt genes are expressed in transgenic Maize Cotton
Potato

116. Insect – resistant transgenic plants expressing plants Bacillus thuringiensis toxins
The production of transgenic plants that express the insecticidal toxins produced by different strains of the soil bacterium Bacillus thuringiensis
Spores of Bt contain a crystaline protoxin protein encoded by a gene Cry carried on a plasmid within the bacteria

117. Ingestion of spores by the insect, the crystal dissolves and the protein is cleaved by digestive proteinases in the insect gut to generate active Bt toxin molecules
Active toxin molecules binds to a specific glycoprotein receptor that is situated in the cell membrane of gut cell lining the insect midgut and then insert it self into the gut cell membrane

118. The bound toxin interacts with the cell that allows the free passage of ions
The toxin created channels destroy the imbalance in ion concentration that has been established across these membranes (gut PH approximately ) resulting in the death and lysis the cells lining of the gut
The bacteria eventually sporulate, releasing fresh spores into the soil to repeat the cycle

120. Plant Pathogens

121. Plant Pests
Pathogens
Predators
Weeds 2

122. Symptoms of Microbial Diseases in Plants
Necrosisنخر - death of plant cells; may appear as spots in localized areas
Canker تقرحات- localized necrosis resulting in lesion, usually on stem
Wilt - droopiness due to loss of turgor
Blight - Loss of foliage
Chlorosis - loss of photosynthetic capability due to bleaching of chlorophyll
Hypoplasia - stunted growth
Hyperplasia - excessive growth
Gall - tumor 8

123. Pathogens : Viruses Transmission of viruses Airborne transmission
Insect vectors - especially aphids, whiteflies, leafhoppers, mealybugs, ants
Nematodes
Seeds from infected parent plants
Airborne transmission
Infected plant parts
Aphids
Pollen 35

124. Pathogens: Bacteria
Generally Gram-negative bacilli: species of Erwinia, Pseudomonas, Xanthomonas, Agrobacterium, and Corynebacterium
Dispersal from plant generally passive by water, wind-blown water, animals, agricultural workers
In warm, humid climates, where dew and rain are common, dispersal of bacteria by rain-splash is the major means of disease spread
Airborne spread on rafts of plant material 38

125. Pathogens: Fungi
Over 70% of all major crop diseases are caused by fungi
Thousands of fungal species recognized as plant pathogens
Fungal diseases cost more than $3.5 billion to US farmers alone
In general spores of most fungal pathogens are adapted for airborne transport 40

126. Plant Pathogenic Nematodes
Obligate parasites
Feed on roots of plants
Some never live in soil, they survive in host and are spread by insect vectors
Reduces crop yield and increases risk of infection through wounds 68

127. Insects Damage or destroy crops before and after harvest
Larval stage often most destructive
Injury plants directly by using plant for food or shelter and indirectly by spreading pathogens 69

128. Basic feeding patterns
Chewing Insects
Either larvae or adults
Tear or bite portions of the plants
May eat their way through the plant causing holes and tunnels
Others eat whole plant
Sucking Insects
Pierce the plant and sucks up the sap
Results in curling, stunting, deformed parts

129. Weeds “Unloved plant” Injurious to agricultural crops
Loss is a direct result of competition for light, water, nutrients

130. Control Measures
Chemicals widely used to control plant pests and diseases
Dangers of pesticide use apparent

131. Integrated Pest Management (IPM)
Multifaceted approach to disease control
Sanitation
Crop rotation
Genetic resistance
Biological Control

133. Thank you for your attention